Dry eye syndrome, or chronic dry eye (CDE) is a chronic lack of sufficient lubrication and moisture in the eye. Its consequences range from subtle but constant irritation to ocular inflammation of the anterior (front) tissues of the eye. The symptoms include persistent dryness, scratching, redness, and burning in the eyes, and some people also experience a foreign body sensation: the feeling that something is in the eye. In CDE, the eye either does not produce enough tears, or produces tears that evaporate too quickly. Sometimes, watery eyes can result from dry eye syndrome, because the excessive dryness over-stimulates production of the watery component of tears. Tears are composed of three layers: the outer, oily, lipid layer; the middle, watery, lacrimal layer; and the inner, mucous or mucin layer. Each layer is produced by a different part of the eye (the lacrimal gland produces the lacrimal layer, for example), so problems with any one of these sources can result in dry eyes.
CDE has several causes. It occurs as a part of the natural aging process, especially during menopause; as a side effect of many medications, such as antihistamines, antidepressants, certain blood pressure medicines, Parkinson's medications, and birth control pills; wearing contact lenses; smoking; or because of a dry, dusty or windy climate. Air conditioning or dry heating systems can also dry out the eyes. Another cause is insufficient blinking, which often occurs in occupations that require staring at computer screens. Incomplete closure of the eyelids, eyelid disease and a deficiency of the tear-producing glands are other causes. Dry eye complaints are occasionally associated with incomplete closure of eyelids following cosmetic eyelid surgery (blepharoplasty). Risk factors for CDE include hormonal changes (related to aging and menopause), medical conditions (e.g., diabetes), and autoimmune disease (e.g., Sjogren's Syndrome).
CDE is an ongoing condition that may not be cured (depending on the cause), but the accompanying dryness, scratchiness, and burning can be managed. Artificial tears, which are lubricating eyedrops, may alleviate the dry, scratching feeling. Restasis® eyedrops (0.05% cyclosporine in a castor oil base) also help eyes increase tear production. Restasis® eyedrops are placed in the affected eye(s) twice a day, about 12 hours apart. These eye drops must be mixed well before use, and the eye drops have a milky white appearance.
Many people attempt to treat their dry eyes with normal eyedrops rather than artificial tears, perhaps because normal eyedrops are significantly less expensive than artificial tears (typically only a fifth of the cost of generic cyclosporine-containing drops), and do not require a prescription. These drops can reduce or temporarily eliminate eye redness, but they do not treat the cause of the redness: whether it is dryness, environmental irritation, or some other problem. Additionally, the vasoconstrictors in common eyedrop formulas, that reduce redness by contracting the eye's blood vessels, lose their effectiveness over time such that more and more is needed to achieve the same effect.
Hence, there remains a need for inexpensive, effective, and long-term medicament for treating CDE.